Those skilled in the art of marine engines are familiar with many different types of cooling systems and many different techniques for removing heat from various heat emitting components of marine propulsion systems. Those skilled artisans are also familiar with many important issues associated with the removal of heat from marine engines. Not only is it important to avoid the overheating of various components and devices of a marine propulsion system, but it is also very important to avoid the removal of too much heat from certain portions of the engine. This is particularly true in marine engines, as opposed to engines used to propel land vehicles, because marine engines often use water from a body of water as its primary coolant and the water taken from lakes, rivers, bays, and oceans are often significantly colder than is desirable for maintaining the best operating temperatures of certain engine components. The use of cold water can often result in the overcooling of certain portions of the engine and, as a result, the condensing of fuel vapor which can dilute the oil supply of the engine with liquid fuel. The disadvantages of oil dilution are well known to those skilled in the art of marine engines as are the various types of damage that can result from it. Other problems associated with cooling marine engines relate to the direction of cooling water as it flows through engine components. Those skilled in the art of marine engines are also familiar with the importance of the sequence with which various engine components are cooled and the shape of the engine components that carry the coolant, such as the water jacket.
U.S. Pat. No. 5,036,804, which issued to Shibata on Aug. 6, 1991, describes a cooling system for a four stroke outboard motor. The cooling system for a four cycle internal combustion engine utilized as a power plant for an outboard motor is described. The cooling system is designed so that coolant is first delivered to cool an exhaust manifold in the cylinder block, then the exhaust port is of the cylinder head and the other cylinder head components and then the cylinder block cooling jacket surrounding the cylinder bores.
U.S. Pat. No. 5,048,467, which issued to Kojima on Sep. 17, 1991, describes a water jacket arrangement for marine two cycle internal combustion engines. An outboard motor having an improved cooling system, wherein liquid coolant is circulated through an exhaust manifold cooling jacket then through a cylinder head cooling jacket and then through an upper portion of the cylinder block cooling jacket, is described. A thermostatic valve controls the flow from the upper cylinder block cooling jacket through a lower cylinder block cooling jacket so as to avoid quenching of the intake charge by coolant which has not reached operating temperature.
U.S. Pat. No. 5,873,330, which issued to Takahashi et al. on Feb. 23, 1999, describes a cooling arrangement for an engine. A cooling system for a vertically oriented engine of an outboard motor is disclosed. Coolant flows through the coolant system from a coolant pump into a coolant jacket surrounding an exhaust manifold of the engine, down to a bottom of a cylinder head of the engine, through a cylinder head, an engine block, through a thermostat, and then to a jacket positioned along an exhaust pipe leading from the exhaust manifold, to a coolant discharge.
U.S. Pat. No. 5,904,605, which issued to Kawasaki et al. on May 18, 1999, describes a cooling apparatus for an outboard motor. The outboard motor is provided with a water cooled engine in a vertical alignment in which a crankshaft is vertically disposed, the engine being composed of a cylinder block, a cylinder head and an exhaust manifold into which water jackets are formed respectively and the water jackets are supplied with cooling water from a water pump disposed below the engine, the cooling apparatus comprising a cylinder cooling water passage for supplying cooling water from the water pump to the water jackets of the cylinder block and the cylinder head. It also comprises an exhaust cooling water passage for supplying cooling water from the water pump to the water jacket of the exhaust manifold, the cylinder cooling water passage and the exhaust cooling water passage being independently disposed from each other and being joined together at downstream portions thereof.
U.S. Pat. No. 6,890,228, which issued to Tawa et al. on May 10, 2005, describes an outboard motor equipped with a water cooled engine. It includes an exhaust manifold cooling water jacket for cooling an exhaust manifold for discharging to the outside exhaust gas from a combustion chamber. The manifold cooling water jacket is supplied with cooling water from a cooling water pump. A water outlet is provided in the highest part of the exhaust manifold cooling water jacket and is made to communicate with a water check outlet for confirming the circulation of cooling water due to operation of the cooling water pump.
U.S. Pat. No. 6,921,306, which issued to Tawa et al. on Jul. 26, 2005, describes a water cooled vertical engine and outboard motor equipped therewith. It includes an exhaust guide cooling water jacket and an exhaust manifold cooling water jacket which are formed in an engine compartment. It also comprises a cylinder block cooling water jacket formed in a cylinder block. Water is supplied from a cooling water pump in parallel to an upper part and a lower part of the cylinder block cooling water jacket through the exhaust guide cooling water jacket and the exhaust manifold cooling water jacket.
U.S. Pat. No. 7,114,469, which issued to Taylor on Oct. 3, 2006, discloses a cooling system for a marine propulsion engine. The system divides a flow of cooling water into first and second streams downstream of a pump. The first stream flows through a first cooling system which is controlled by a pressure sensitive valve. The second stream flows through a second cooling system which is controlled by a temperature sensitive valve.
U.S. Pat. No. 7,264,520, which issued to Taylor et al. on Sep. 4, 2007, discloses a cooling system for an outboard motor having both open and closed loop portions. The system pumps water from a body of water through certain selected portions of the outboard motor and through a heat exchanger which, in turn, comprises a coolant conduit that is directed to conduct the coolant in thermal communication with various portions of the outboard motor. The engine block is cooled by a flow of the coolant and an engine head is cooled by a flow of water from the body of water. Other head emitting devices are connected in thermal and fluid communication with the water and coolant conduits.
U.S. Pat. No. 7,318,396, which issued to Belter et al. on Jan. 15, 2008, discloses a cooling system for a marine propulsion engine. It incorporates first and second thermally responsive valves which are responsive to increases in temperature above first and second temperature thresholds, respectively. The two thermally responsive valves are configured in serial fluid communication with each other in a cooling system, with one thermally responsive valve being located upstream from the other.
U.S. Pat. No. 8,783,217, which issued to Taylor et. al. on Jul. 22, 2014 discloses a method and apparatus for cooling an engine of a marine propulsion engine wherein water is directed to flow in two opposing directions through the cylinder head of the engine. In certain embodiments, water is directed to flow away from the engine, from a point sequentially between the exhaust manifold and the cylinder head, in order to remove heat from the exhaust manifold without allowing that heat to raise the temperature of other portions of the engine.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be beneficial if a cooling system for a marine engine could remove heat from selected portions of the engine system and avoid the entrapment of air pockets within the coolant flow that could otherwise result in the overheating of local regions of the engine system.
The present application discloses a system for cooling an engine of a marine propulsion system. The marine propulsion system generally includes an engine having a cylinder block an exhaust manifold that conveys hot exhaust gases from the engine, a pump that pumps water from a body of water in which the marine propulsion system is operating to cool the hot exhaust gases in the exhaust manifold, a water jacket surrounding the exhaust manifold, and at least one conduit on the water jacket discharging at least one stream of water for cooling the engine.
The water jacket surrounding the exhaust manifold conveys water along at least one stream having a cross sectional area for cooling the hot exhaust gases in the exhaust manifold. At least one portion of the water jacket includes at least one converging passageway where an outer wall of the water jacket tapers inwardly to reduce the cross sectional area of the stream of water as water travels from the pump to the outlet conduit. In other embodiments, the water jacket conveys water along two streams of water. The two streams of water may diverge at an entry point from the pump to the water jacket such that the streams travel in opposite directions. In this embodiment, the two streams of water may converge at the outlet conduit, or may exit at separate outlet conduits. In the embodiment where two streams exit at a first and second outlet conduit, the first and second outlet conduits may be spaced from one another such that the two water streams do not converge. In further embodiments, the water jacket may comprise at least two converging passageways. In the embodiment with two streams of water, each stream of water may include a converging passageway.
The present application further contemplates a system for cooling an engine of a marine propulsion system, the system including an engine having a cylinder block and a cylinder head, an exhaust manifold that conveys hot exhaust gases from an engine, a pump, a water jacket surrounding the exhaust manifold, and at least one outlet conduit on the water jacket discharging water for cooling the engine. The pump pumps water from a body of water in which the marine propulsion system is operating to cool the exhaust gases in the exhaust manifold and to cool the engine.
The water jacket has a cross sectional area, defined in part by an inner wall and an outer wall for conveying water along at least one pathway for cooling the hot exhaust gases in the exhaust manifold. At least one section of the water jacket pathway includes a first flow portion, a second flow portion, a third flow portion and fourth flow portion. The inner wall and outer wall of the first flow portion of the water jacket are parallel. In the second flow portion, the outer wall and the inner wall diverge from parallel. In the third flow portion, the outer wall and the inner wall converge to parallel. The second and third flow portions define at least part of a converging passageway that reduces air pockets in the conveyed water. In the fourth flow portion, the inner wall and the outer wall are parallel. In one embodiment, the outer wall of the water jacket tapers inwardly to reduce the cross sectional area of the water flow pathway in the third flow portion.
Again, the water jacket may convey water along two pathways that diverge at an entry point from the pump to the water jacket, such that the streams travel in opposite directions. The pathways may converge at an outlet conduit, or may exit at a first and second outlet conduit, wherein the first and second outlet conduits are spaced from one another such that the two streams do not converge. In these embodiments, the water jacket pathway may include at least two flow sections, with each flow section having a first flow portion, a second flow portion, a third flow portion and a fourth flow portion.
In another embodiment of the present application, a water jacket for cooling and exhaust manifold that conveys hot exhaust gases from an engine in a marine propulsion system is contemplated. In this embodiment, the water jacket comprises an inlet conduit receiving water from a pump that pumps water from a body of water in which the engine is operating. The water may include entrained air in the form of air pockets or bubbles. The water jacket further comprises an outlet conduit discharging water for cooling the engine and a water flow passage extending from the inlet conduit to the outlet conduit. The water flow passage has a cross sectional area defined by an outer wall, an inner wall, a top wall and a bottom wall. The water flow passage surrounds the exhaust manifold with the water flowing through the passage to cool hot exhaust gases in the exhaust manifold. The water flow passage includes at least one section wherein the outer wall converges with the inner wall to reduce the cross sectional area of the pathway. The water jacket may comprise at least two water flow passage sections wherein the outer wall and inner wall will converge to reduce the cross sectional area along a portion of the pathway. Each water flow passage section may further comprise a first flow portion, a second flow portion, a third flow portion and a fourth flow portion. The inner wall and outer wall of the first flow portion are parallel. In the second flow portion, an outer wall diverges from parallel relative to the inner wall. In the third flow portion, an outer wall and the inner wall converge to parallel. In the fourth flow portion, the inner wall and outer wall are again parallel. The converging flow section of the water jacket reduces the air pockets present in the water to provide even cooling of the exhaust manifold.